The invention relates to a seat rail structure for a motor vehicle and more particularly to seat rail structure in which a slide rail connected to the vehicle seat is guided on a guide rail secured to the vehicle frame.
Under normal conditions, the known seat rail structures of this kind readily meet normal safety requirements. The forces occurring under normal driving conditions which are passed from the seat base through the slide rail into the guide rail are safely absorbed by the guide rail without deformations being caused. Whether the vehicle seat will remain in its fixed position under extreme conditions, i.e., in a crash, does, however, depend decisively on the effectiveness of the safety-belt retaining system associated with the vehicle seat. With the known seat rail structures, it is to be assumed that in an impact the vehicle seat will only retain its fixed position through the seat rail structure if the points at which an effectively operating retaining system is anchored on the vehicle are remote from the seat and the seat rail structure, for example, on the floor and the beam of the vehicle as the inertia forces generated during the impact will be predominantly absorbed directly by the vehicle at the anchoring points of the retaining system and, therefore, will not only act on the guide rail through the slide rail. For various reasons, it is however, desirable to provide at least one anchoring point or the anchoring of the retaining system directly on the vehicle seat. In this case, the total inertia forces resulting from the mass of the seat itself and the mass of the seat user when accelerations occur, or a considerable part of these inertia forces must be kept under control by the seat rail structure. In view of the high accelerations occurring in crashes and the resulting, very high inertia forces, the load bearing capacity of the rails is usually inadequate, at least when the load conditions are unfavorable and the vehicle is subjected to hard impact. This may result in sagging of the rails which, in turn, may cause the slide rail to be torn out of the guide rail.